1. Field of the Invention
Embodiments of the invention generally relate to apparatus and methods for performing reverse flow (e.g. cementing) operations. In particular, embodiments of the invention relate to a reverse flow (e.g. cementing) valve.
2. Description of the Related Art
One or more casings may be cemented in a wellbore by utilizing what is known as a reverse cementing method. The reverse cementing method comprises pumping conventionally mixed cement into the annulus between the casing string and an existing string or an open hole section of the wellbore. As the cement is pumped down the annular space, drilling or other wellbore fluids ahead of the cement are displaced around the lower ends of the casing string and up the inner bore of the casing string and out at the surface. A predetermined amount of cement is pumped into the annulus to ensure a good quality cement job.
In some wellbore completion operations, such as a multi-zone open hole (MZOH) completion, a work string comprising a fracturing sleeve and one or more packers may be used to conduct a fracturing operation to treat or stimulate the formation surrounding the well. It is generally desired to cement the vertical section of the wellbore above the area where the fracturing operation is to take place, without passing any cement through the fracturing sleeve or packers. The cementing operation should be done without creating additional leak paths through the work string, or compromising the work string integrity above the packers. The operation should also be done without the requirement for any drill-out operations between cementing and fracturing, which increase the time and cost of the overall completion operation. Other operational considerations include the necessity to displace drilling or other wellbore fluids prior to or while cementing, and the desire to initiate operation of one or more tools on the work string by deploying a single ball into the flow through the work string, and then use only fluid flow (e.g. no intervention devices or further actuation devices such as balls) for additional operational stages.
Historically, although reverse cementing has been used to keep cement out of the work string, prior reverse cementing methods typically either create a leak path in the work string for fluid flow such as with use of a port collar, or cannot be run with fracturing sleeves in place. Stage collars have been used, but they require a drill-out operation after use and are not as robust as standard threaded connections. Another less than ideal solution has been to cement the entire wellbore, and to use fracturing sleeves that require mechanical intervention for actuation rather than standard ball actuated sleeves.
Therefore, there exists a need for new and improved methods and apparatus for conducting reverse flow or cementing operations.